Because the surface mount oscillator is small and light, it is widely adopted as a reference source of frequency and time, particularly in portable electronic equipment. Recently, the consumption of surface mount oscillators is increasing in response to an information-intensive society, and a surface mount oscillator with high productivity and high quality has been desired. As one such surface mount oscillator, there is a surface mount oscillator in which a base and a cover are bonded to opposite principal surfaces of a crystal plate, whose oscillating part is surrounded by a frame.
FIG. 8 to FIG. 10 are diagrams for explaining one conventional example of the surface mount oscillator. FIG. 8 is a perspective view thereof, FIG. 9 (a) is a plan view of one principal surface of a framed crystal plate, FIG. 9 (b) is a plan view of the other principal surface of the crystal plate, FIG. 10 (a) is a plan view of one principal surface of a base, and FIG. 10 (b) is a plan view of the other principal surface of the base.
As shown in FIG. 8, a surface mount oscillator 1 in the conventional example is formed by bonding a base 3 made of ceramic and a cover 4 made of Kovar to opposite principal surfaces of a framed crystal plate 2.
Moreover, as shown in FIG. 9, the framed crystal plate 2 includes an oscillating part 6 having a first excitation electrode 5a and a second excitation electrode 5b on the opposite principal surfaces, a frame 7 surrounding the oscillating part 6, and a first connecting part 8a and a second connecting part 8b that extend from opposite sides of one end of the oscillating part 6 to connect the oscillating part 6 with the frame 7. Frame notches 9a to 9d are fowled at four corners on an outer periphery of the frame 7 in a planar view.
As shown in FIG. 9, the first excitation electrode 5a facing the cover 4 is electrically connected to a frame metal film 11a formed on a principal surface of the frame 7 facing the cover 4, via an electrically-conducting path 10a formed in the first connecting part 8a. On the other hand, the second excitation electrode 5b facing the base 3 is electrically connected to a frame metal film 11b formed on a principal surface of the frame 7 facing the base 3, via an electrically-conducting path 10b formed in the second connecting part 8b. 
The frame metal films 11a and 11b are formed, as shown in FIG. 9, over the whole periphery of the frame 7. As shown in FIG. 9 (a), the frame metal film 11a is electrically connected to frame end-face electrodes 12a and 12b formed on the side portions of the frame notches 9a and 9b. Further, as shown in FIG. 9 (b), the frame metal film 11b is formed away from the frame notches 9a to 9d, and is not electrically connected to the frame end-face electrodes 12a and 12b. 
The framed crystal plate 2, the cover 4, and the base 3 are bonded by using a eutectic alloy (for example, AuGe) formed on the surfaces of the frame metal films 11a and 11b. 
As shown in FIG. 10, base notches 13a to 13d are formed at four corners of the base 3 in a planar view. The base notches 13a to 13d respectively correspond to the frame notches 9a to 9d formed in the crystal plate 2.
Moreover, as shown in FIGS. 10 (a) and (b), a base metal film 14 is formed to face the frame metal film 11b formed in the crystal plate 2. The frame metal film 11b and the base metal film 14 are electrically connected to each other via a eutectic alloy. The base metal film 14 is formed away from the base notches 13a and 13b. However, the base metal film 14 is extended to the base notches 13c and 13d and electrically connected to base end-face electrodes 15c and 15d formed on the side portions of the base notches 13c and 13d. 
As shown in FIG. 10 (a), the base end-face electrodes 15c and 15d are electrically connected to a mounting terminal 16b formed on the principal surface of the base 3 serving as an external bottom face of the surface mount oscillator 1. The mounting terminal 16b is formed at one end of the principal surface of the base 3, and a mounting terminal 16a is formed at the other end thereof. The mounting terminal 16a is electrically connected to the frame end-face electrodes 12a and 12b via the base end-face electrodes 15a and 15b formed on the side portions of the base notches 13a and 13b. 
Electrical connection of the surface mount oscillator in the conventional example can be summarized as follows. That is, the first excitation electrode 5a shown in FIG. 9 is electrically connected to the mounting terminal 16a via the electrically-conducting path 10a, the frame metal film 11a, the frame end-face electrodes 12a, 12b, and the base end-face electrodes 15a, 15b. The second excitation electrode 5b is electrically connected to the mounting terminal 16b via the electrically-conducting path 10b, the frame metal film 11b, the base metal film 14, and the base end-face electrodes 15c, 15d.     [Patent Document 1] Japanese Unexamined Patent Publication No. 2000-223996